In fluid flow designs for high pressure industrial applications, for example, high pressure fluid flow through a valve may create forces which tend to close the valve, particularly when the valve is in or near a fully closed position. This flow force increases the actuation force required to stroke or open the valve. Fuel admission systems for use with large internal combustion engines in industrial or mobile applications may involve significantly high pressures and flow rates. Generally, mechanically and/or hydraulically actuated valves have been used to achieve the actuation forces sufficient to overcome the high pressures at the valve, which tend to urge the valve toward the closed position. Due to force limitations, electrically actuated valves generally produce lower actuation forces than that achieved with mechanical and/or hydraulic actuators. As a result, electrically actuated valves have typically not been used with large engines in industrial or mobile applications requiring high actuation forces.
Electrically actuated valves have been known to provide fast, reliable actuation, which is advantageous in internal combustion engines used in industrial or mobile applications. In such applications, the ability to control the admission of fuel to each cylinder of a multiple cylinder engine precisely and independently may result in balanced firing of all of the engine cylinders. As a result, engine vibrations and engine wear may be reduced, and efficient engine operation may be achieved. In addition, balanced firing may result in improved fuel economy and reduced emissions. Therefore, improved engine operation may be achieved in engine applications by using an electrically actuated valve to control fuel admission in which the actuation force for stroking or opening the valve is reduced.
In addition to the force limitation issues associated with electrically actuated valves, a problem in the operation of these valves can result when an engine operator or engine system rapidly rejects load. This may occur when the operator or system rapidly throttles down the engine from a high load condition to an essentially no-load condition at which no power is required or being drawn from the engine or system powered by the engine. In such situations, the engine intake manifold pressure falls quickly, in as little as a fraction of a second.
The rapid load reduction promotes the rapid closure of the engine throttle to maintain engine speed. Such rapid throttle closure results in a dramatic drop in intake manifold pressure, reducing the pressure on the downstream side of the valves below their normal operating pressure. However, as the upstream side of the valves are still exposed to high pressure fluid (fuel), the pressure differential across the movable metering plates and movable portions of the valves increases. As noted above, the pressure across these valves is already high, and the valves are already configured to operate proximate a threshold differential pressure which must be overcome by the actuation systems of the valves. Unfortunately, this spike in pressure differential due to the drop in intake manifold pressure at the (fuel admission valve outlet) can lock the valves in their closed position and prevent them from being opened via their actuation systems. Such locking of the fuel admission valves will then stall engine operation until normal valve function is restored. Further amplifying this problem is the lack of a simple way to release the pressure on the high pressure side of the valve to unlock the valve.
While there have been attempts to add supplemental pressure relief arrangements to address this valve lock-up problem, this adds complexity and expense to the fuel admission system. Further, many of these fuel admission systems are restricted in size. In such applications, the pressure relief arrangements designed to address this problem cannot be installed due to insufficient space.
The present invention relates to improvements over the current state of the art for fuel admission valves.